The PHP.net site reports three new versions of various revisions of the language being released all at once, all fixing an OpenSSL issue announced in CVE-2013-6420. This includes updates for all three supported versions:

PHP 5.4.23

PHP 5.3.28 (also fixes CVE-2013-4073)

PHP 5.5.7

As this is a security-related issue, it's recommended that you update to the latest version for your installation. You can get these latest downloads from either the main downloads page or for Windows users, windows.php.net.